Determination of prostate gland volume by transrectal ultrasound: correlation with radical prostatectomy specimens

Estimation of the prostate gland volume employing transrectal ultrasound provides important additional information in patients with benign and malignant diseases of the prostate. Twenty-five patients underwent transrectal ultrasound of the prostate prior to radical prostatectomy for organ-confined cancer of the prostate. The prostate gland volume was calculated employing two different methods. The prostate specimen weights were compared with the results of each of the volume estimation method. The prolate ellipse formula, widely used as an alternative to planimetry, demonstrated a correlation coefficient of r2 = 0.831. However, a variation of the prolate ellipse formula expressed as (width x width x height) x pi/6, which is easier to perform as described by Terris and Stamey, exhibited a correlation coefficient of r2 = 0.829. It appears to be a reliable means of estimating prostate gland volume, especially in cases in whom the original formula is difficult to apply.